ICAO Airspace Classes A to G
General (ICAO)
ICAO Annex 11 defines 7 airspace classes (A through G), graded by ATC service level. Details in SERA Appendix 4.
Overview — controlled vs uncontrolled
E, B, D, A, C are classes of controlled airspace:
- A, B, C, D, E = controlled (ATC provides service).
- F, G = uncontrolled.
Class table (standard, VFR-relevant)
| Class | VFR | Separation VFR vs IFR | Service VFR | Radio |
|---|---|---|---|---|
| A | Not allowed | — | — | — |
| B | Permitted | Separated | ATC clearance + separation | Mandatory |
| C | Permitted | Separated from IFR | Traffic info VFR/VFR + separation VFR/IFR | Mandatory |
| D | Permitted | Not separated | Traffic info VFR/IFR + VFR/VFR | Mandatory |
| E | Permitted | Not separated | Traffic info as far as possible | Optional |
| F | Permitted | Advisory | AAS | Optional |
| G | Permitted | None | FIS on request | Optional |
Class B
Minimum visibility at 5000 ft in class B for VFR flights is 5 km. Distance from clouds 300 m vertical / 1500 m horizontal.
Class C
Continuous radio monitoring on the frequency of the appropriate ATC unit is obligatory for visual flights in airspace C.
In airspace C, VFR flights are separated from IFR flights as far as possible. Air traffic advisory service is provided.
Class C VMC: visibility 8 km at and above FL 100 / 5 km below FL 100; cloud distance 300 m vertical / 1.5 km horizontal; max 250 kt IAS below FL 100; ATC clearance; radio monitoring; separation from IFR; ATC; traffic information VFR/IFR (evasion recommendations on request).
Radio loss in class C
If radio contact is lost before entering airspace C and after reception of the entry clearance, airspace C has to be avoided despite the entry clearance.
When radio contact is lost in airspace C below FL 100 near international aerodromes, the pilot must exit the airspace via the shortest route under VFR if unable to continue per the last acknowledged ATC clearance.
VMC loss in class C
If a VFR pilot in airspace C (below FL100) can no longer maintain VMC, he must inform ATC immediately and request a new clearance (e.g. climb, descent, or heading change) that restores visual flight conditions.
Transponder failure in class C
In case of a transponder failure within airspace C, the pilot has to inform the appropriate ATC unit immediately.
Class D
In VMC in airspace D, a VFR flight receives traffic information about IFR flights (evasion recommendations on request) and traffic information about other VFR flights.
Class E
Airspace E begins at 1000 ft AGL and 1700 ft AGL, otherwise 2500 ft AGL, and reaches up to FL 100.
Flight visibility 5 km. Horizontal cloud distance 1.5 km, vertical 1000 ft.
Transponder code A/C 7000 has to be set by own accord by powered aircraft on VFR flights in airspace E above 5000 ft AMSL or above 3500 ft AGL, whichever is higher.
VFR flights can expect traffic information, as far as possible, in airspace E.
VFR traffic is not separated from any other traffic.
Class G — uncontrolled
VFR flights are not required to continuously monitor the radio frequency in airspace G and D:
- Below 3000 ft MSL / 1000 ft AGL: ground in sight continuously; flight visibility ≥ 1.5 km if IAS < 140 kt; clear of clouds.
- Above 3000 ft AMSL / 1000 ft AGL: visibility 5 km, cloud distance 1500 m horizontal / 1000 ft vertical.
- Flight visibility 800 m below 3000 ft AMSL or 1000 ft AGL — special case.
Formation flying — uncontrolled only
Aircraft may only be flown in formation in uncontrolled airspace after previous agreement of the pilots.
Restricted areas
Restricted areas are airspace where crossing is subject to restrictions.
Europe (EASA / EU)
SERA Appendix 4 defines class requirements in the EU — equivalent to ICAO Annex 11.
Germany (national)
In Germany:
- Class A is not used.
- Control zones are classified as airspace D.
- Class C from FL100 up to FL245 (standard).
- Class E below class C down to 2500 ft AGL.
- Class G below.
In Germany, airspaces D, RMZ, TMZ, D control zone are applied according to SERA or ICAO.
TMZ (Transponder Mandatory Zone)
Before entering a TMZ the transponder needs to be switched on and mode A and C or mode S is to be activated.
RMZ (Radio Mandatory Zone)
An RMZ is an airspace class G.
In order to enter an RMZ, continuous monitoring of the radio frequency is required after the initial call before entry until leaving the zone.
In a Radio Mandatory Zone (RMZ), when hearing an IFR flight approaching the runway, a VFR pilot should visually scan for the incoming aircraft in the direction of its approach to ensure safe separation, as IFR traffic does not automatically evade VFR.
ATZ (Aerodrome Traffic Zone)
An ATZ is an element of the airspace surrounding an uncontrolled airfield to protect the nearby air traffic.